The optimum design of multivariate acceptance sampling plans

A model is developed which may be used to determine the expected total cost of quality control per inspection lot under acceptance sampling by variables where several characteristics are to be simultaneously controlled. Optimization of the model is accomplished through the application of a conventional search procedure. The sensitivity of the model and the optimum solution to the shape of the underlying probability distributions is discussed and associated analyses are presented through an example.     

Dominating sets for rectilinear center location problems with polyhedral barriers

In planar location problems with barriers one considers regions which are forbidden for the siting of new facilities as well as for trespassing. These problems are important since they model various actual applications. The resulting mathematical models have a nonconvex objective function and are therefore difficult to tackle using standard methods of location theory even in the case of simple barrier shapes and distance functions. For the case of center objectives with barrier distances obtained from the rectilinear or Manhattan metric, it is shown that the problem can be solved in polynomial time by identifying a dominating set. The resulting genuinely polynomial algorithm can be combined with bound computations which are derived from solving closely connected restricted location and network location problems. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 647–665, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10038     

The long term effects of an aging fleet on operational availability and cost: evidence from the U.S. coast guard

This paper empirically examines whether the aging of a fleet affects operational availability and operating cost using a unique data-set on the 117 47-foot Motor Lifeboats (MLBs) of the United States Coast Guard (USCG). Procured from 1997 to 2003, the 47-foot MLB is the standard lifeboat of the USCG and all 117 MLBs remain in service. The aging of the MLB fleet has resulted in higher annual operating costs and lower operational availability, although the nature of this relationship remains unclear. Our estimation strategy utilizes an error components estimator to examine these issues. We employ three variants of the dependent variables (i.e. the standard logarithmic transformation as is most commonly seen in the literature, inverse hyperbolic sine [IHS], and level outcomes). The point estimates from the standard logarithmic model finds operational availability for the MLBs decreases at a rate between 0.83 and 1.8% per year and cost increases at a rate between 0.33 and 7.81% per year. Similar effects are shown with the IHS and level outcome specifications. In terms of nonlinearity effects, we find the most pronounced changes in operational availability and cost occur for MLBs aged 15 years or more (in comparison to younger MLBs).     

The elephant in the room

When United States (US) President Barack Obama announced in 2013 that he would host the first United States-Africa leaders' summit the next year, he was greeted with considerable scepticism. Many critics thought he was just playing catch-up with other countries and organisations which had been holding Africa summits for years, especially China. But, whatever the motives, the event itself proved to be a substantial success, probably re-setting US relations with Africa for many years to come.     

Use it or lose it: On the incentives to spend annual defence operating budgets

In most western countries, there is a strong incentive for defence department budget-holders to expend all of the funds they are authorized to spend in a fiscal year. In this paper, we question whether this emphasis makes sense. We develop a model of a defence department’s operating expenditure assuming a fixed level of funding for a year and uncertain costs. The results of the model suggest that the incentive for departmental managers to expend all authorized funds is inefficient. We explore the implications of the model for the Department of National Defence (DND) in Canada in light of the recent criticism of DND lapsed funding by the Auditor-General of Canada.     

RAIN,GROWTH, AND CIVIL WAR: THE IMPORTANCE OF LOCATION

We re‐examine the Miguel et al. (2004 Miguel, E., Satyanath, S. and Sergenti, E. 2004. Economic shocks and civil conflict: an instrumental variables approach. Journal of Political Economy, 112(4): 725–753. [Crossref], [Web of Science ®] , [Google Scholar]) study of the impact of growth on civil war, using growth in rainfall as an instrument. Miguel et al. (2004 Miguel, E., Satyanath, S. and Sergenti, E. 2004. Economic shocks and civil conflict: an instrumental variables approach. Journal of Political Economy, 112(4): 725–753. [Crossref], [Web of Science ®] , [Google Scholar]) – in our view, erroneously – include countries participating in civil wars in other states. Restricting the conflict data to states with conflict on their own territory reduces the estimated impact of economic growth on civil war. We show how spatial correlations in rainfall growth and participation in civil conflicts induce a stronger apparent relationship in the mis‐classified data.     

SUICIDE TERRORISM AND THE BACKLASH EFFECT

This paper presents a game‐theoretic model of suicide terrorism containing three agents: the terrorist leader; a targeted government; and potential terrorist supporters. Supporters join the terrorist group if they gain more from their participation than from their economic opportunities. Preemptive measures by the government can result in a backlash that encourages recruitment through new grievances. Suicide attacks can also lead to recruitment. Increases in preemption costs and/or economic opportunities can reduce the overall level of terrorism, while increasing the proportion of suicide to normal attacks. An increase in the effect of preemption on recruitment, or the propaganda effect of suicide bombings has the opposite effect of increasing normal and suicide attacks, but decreasing the proportion of suicide to normal attacks in the terrorist organization’s strategy profile.